One of the keys to Chelsea's success this season, was the outstanding performances of their defense. From right to left, front to back, Chelsea's defense was solid in all facets. Ivanovic out performed expectations, while also getting in on the scoring. Gary Cahill put in another solid season, forming a formidable partnership with stalwart John Terry. Terry himself continues to prove he's in fact ageless, playing every minute of the Barclay's Premier League campaign. Furthermore, Cesar Azpilicueta did another brilliant job playing left back, keeping his spot over Filipe Luis despite playing on the wrong side of the pitch.

Even Chelsea's substitutes played a large part in the campaign with the likes of Kurt Zouma depicting his wealth of potential, and Filipe Luis showing his class and consistency on the left. Considering all of the Blues success this season, it's tough to see Mourinho making many changes to the defense.

I don't think that Jose Mourinho's intention when he bought the left back, was to make him an expensive backup for Azpilicueta. However, the Spaniard has been unbeatable on the left, leaving little room for Luis in the lineup. Therefore, Mourinho could sell Luis, getting the money back that he spent and allowing him to reinvest in another area in the squad. This would allow Luis to gain more playing time. So why is this the wrong move?

In an earlier article, I spoke about the importance of squad depth, especially when competing on 4 different fronts. Luis is the ultimate squad player. He has a three year deal with the Blues, and unless a team grossly overpays for his services, Mourinho should hold onto the Brazilian at all costs. Luis offers so much to Chelsea.

First and foremost, he provides a different look to Azpilicueta at left back. While the Spaniard tends to be one of the most solid fullbacks in the game, Luis has an attacking edge to his game. Azpilicueta balances the team, staying back, allowing Ivanovic to get forward on the other side. Furthermore, the Spaniard's one-on-one defending is impeccable. However, what he doesn't do well is helping to get forward. People may argue that with Hazard playing in front of him, that he doesn't need to get forward, but a squad can never have too many attacking threats. When Luis has played, he's gotten forward, and played dangerous crosses with his left foot, something that Azpilicueta is simply incapable of, given his stronger foot is his right. Luis is also a deadly free-kick taker, along with a pretty decent shot in general for a full back. While Azpilicueta may close it down in the back, Luis does a good job defending, but also getting forward.

Moving on, Luis represents a sub for both Ivanovic and Azpilicueta. Therefore, if fatigue or injury keeps either player out, Luis can come in, either replacing Azpilicueta, or pushing him over to right back for Ivanovic and allowing Luis to slot in on the left. This is also why Azpilicueta is also so valuable, being able to play on either side.

Luis is also becoming one of the more senior members of the squad. He's someone who's been around the block, performing admirably for years at his position. He's someone that the younger players can look to for guidance and mentorship, especially Azpilicueta. With the older players being fazed out at Chelsea, Luis remains one of the most experienced players, and his leadership on and off the field is invaluable.

Overall, while it seems plausible to allow Luis to move onto greener pastures, it makes so much more sense to hold onto the Brazilian. Even though he's been unable to dispense Azpilicueta at left back, there are so many intangibles he brings to Chelsea that make him an invaluable member of the squad. He adds several pieces to a puzzle that should be even more successful next season. If Chelsea are to go deep in all 4 competitions, they will need reliable squad players, and Luis is probably the best backup in the world.